Hydrogen is a relatively cheap and clean fuel material which can be utilized in engines, fuel cells, and the like. Unfortunately, the storage of hydrogen in gaseous form presents many practical problems and such storage has, to all intents and purposes, been considered impractical for non-stationary uses because of the need for storing the hydrogen in heavy high-pressure cylinders.
Another approach which has received a great deal of attention is the use of reversible metal hydrides. It is well known that many metals form hydrides upon exposure to hydrogen under certain conditions of temperature and pressure and, upon combined conditions of lower pressure and higher temperature, are induced to dissociate into the metal and hydrogen itself. One of the best known and practical of these metals is magnesium which forms the hydride MgH.sub.2. The starting material, magnesium, is cheap and provides a very high storage concentration of hydrogen per unit mass. Unfortunately, the mode of preparation of the hydride requires rather high pressures and temperatures and the uptake is rather slow. Furthermore, it is stable at ambient temperatures and rather high temperatures are required to dissociate the hydride to release the combined hydrogen. This stability has two disadvantages. First, outside forces of heat are necessary to generate "start up amounts" of hydrogen before the heating process can be self-sustained; and secondly, there is a substantial wastage involved in keeping the hydride at a temperature high enough to generate the desired quantities of hydrogen. Other hydrides have also been investigated. These include the mixed hydrides of lanthanum and nickel, of iron and titanium, and vanadium. Certain alloys of cerium known as mischmetal pentanickel have also been investigated. Unfortunately, most of these hydrides have a comparatively low storage capacity and low decomposition temperatures. It would be desirable therefore to provide a hydrogen storage material with the stability and storage capacity of magnesium hydride while still being able to provide sufficient hydrogen at relatively low temperatures for start up purposes.